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Radar and the Horizon

Q. Why does the horizon create an obstacle for shipborne radar? IE. Ships utilising conventional radar can't detect other ships that are beyond the horizon (as seen from the transducer). What's the FE explanation for that?

A. Signal Noise Ratio. Also the power of the radar's return signal diminishes by a power of four in relation to the radar's output. Higher frequency waves (not higher powered) are prone to more "scatter" due to moisture in the air. A higher the transmitter and receiver are located, the less of the atmospheric gradient they are passing through and hence they can "see" farther" before the scatter reduces the power to irretrievable levels. A higher frequency radar beam will naturally diminish faster than a low one as well. In fact, a low frequency beam will travel much farther than the "curvature" of the earth would allow in RET.